An immunomodulatory feed additive enhances in vitro viral vaccine recall antigen responses in dairy heifers.

Enhancing immunological responses to vaccination is an important goal in many herd health management systems. OmniGen-AF®(OG) is an immunomodulatory feed additive that has been shown to enhance innate immune function in ruminants and its effects on adaptive immunity require additional study. The objective of this study was to evaluate post-vaccine antibody titers and circulating cellular memory development in heifers fed OG and administered a commercially available modified-live bovine respiratory disease (BRD) vaccine. Twenty-four Holstein heifers were assigned to one of two diets for 170 days: Control TMR (CON; n = 11), or TMR plus OG (TRT; 9 g/100 kg BW/day; n = 13). Samples for hematology, serology, and cellular assays were collected on D-110, 0, 21, 42, and 60 of the trial. Heifers were administered two priming doses of a modified-live BRD vaccine, with a third dose given on D0. There were no significant differences in total WBC and absolute number or the percentage of circulating lymphocytes, monocytes, neutrophils, RBC, or platelets on D-110 through D21. On D42 and D60, CON had significantly higher numbers of lymphocytes. On D0, mean serum neutralizing (SN) titer to BHV-1 was significantly higher for CON compared to TRT. SN titers were not significantly different between CON and TRT at any other time point for BHV-1, BVDV type 1, or BVDV type 2. TRT mounted a significantly stronger recall proliferative response to 0.5 multiplicity of infection (MOI) of BHV-1, BVDV type 1 and BVDV type 2 on D42 and D60; 0.25 MOI of BVDV type 1 on D21 and D42; and 0.25 MOI BVDV type 2 on D42 compared to CON. IL-4 production induced by 0.5 and 1.0 MOI BHV-1 (D42 and D60); 0.25 MOI of BVDV type 1 (D21); and 0.25 and 0.5 MOI of BVDV type 2 (D60) were significantly higher for TRT than CON. IL-17 production induced by 0.25 MOI of BVDV type 1 was significantly higher on D60 for TRT compared to CON. IFN-gamma and IL-10 were not significantly different between treatments. These data indicate feeding OG has a beneficial effect on responses to vaccine antigens in Holstein dairy heifers.

Effects of an immunomodulatory feed additive on intramammary infection prevalence and somatic cell counts in a dairy herd experiencing major health issues.

A trial was conducted to determine if feeding OmniGen-AF® (OG) to 22 late lactation cows 60 days prior to and during the early dry period, a time of increased susceptibility to mastitis, could reduce disease incidence in a dairy herd experiencing major health issues. Treated cows (n = 11) consumed a ration containing OG [9 g/100 kg of body weight/day] beginning 60 days before dry-off, during the dry period, and through 30 days in milk (DIM). Control cows received the same ration during the dry period through 30 DIM only. Body weights, body condition scores (BCS), intramammary infection (IMI) prevalence, new IMI rates, somatic cell counts (SCC), milk yield, and adverse health events were measured. No differences were found between treatments for body weight or BCS. Adverse health event data at calving showed no differences between treatments except for percentage of cows with hyperketonemia, which was lower among treated cows (63.6% vs 100%). Prevalence of IMI from calving through 30 DIM for treated cows (6.1%) was lower than controls (11.05%); likewise, new IMI rate during this time for treated cows (0.61%) was lower than controls (5.81%). The SCC from calving through 30 DIM for treated cows (215,000/ml) was lower than controls (493,000/ml). Average production/day at the first DHIA test (~33 DIM) showed that treated cows produced more milk (39.9 kg) than controls (35.34 kg). In conclusion, feeding OG 60 days prior to dry-off reduced hyperketonemia and mastitis, lowered SCC, and numerically increased milk yield in a dairy herd experiencing major health issues.

Modulation of innate immune function and phenotype in bred dairy heifers during the periparturient period induced by feeding an immunostimulant for 60 days prior to delivery.

The purpose of this study was to evaluate the effect of a feed additive (OmniGen-AF(®), reported to have immune modulating activity) on innate immunity and health events during the periparturient period in dairy heifers when immunity is suppressed. From 60 days prepartum through calving, supplemented heifers (n=20) received OmniGen-AF(®) daily and were compared with unsupplemented controls (n=20). Blood leukocyte innate immune activity (phenotype markers, phagocytic activity, and reactive oxygen species--ROS production) was measured prior to feeding (60 days prepartum), 30 days later, and on days 1, 7, 14, and 30 postpartum. Adverse health events (udder edema, ketosis, displaced abomasum, and death) and milk production were measured at calving and into early lactation. The fraction of leukocytes with measurable CD62L (L-selectin) on their surface from supplemented heifers tended to be greater during the periparturient period in treated heifers than controls (p=0.100). Likewise, leukocyte phagocytosis of Escherichia coli and Staphylococcus aureus during this time period tended to be greater in heifers supplemented with OmniGen-AF(®) (p=0.100). Conversely, ROS production in response to phorbol myristate acetate or when leukocytes were stimulated with killed S. aureus lysate tended to be greater among control heifers compared with supplemented animals (p=0.100). Supplemented heifers exhibited fewer incidents of udder edema than controls (p=0.030) and tended to exhibit a lower rate of new cases of mastitis (p=0.098); however, no differences were observed in milk somatic cell counts or level of milk production. Results demonstrate a positive role of OmniGen-AF(®) in amplifying leukocyte function consistent with antibacterial activity during the periparturient period, and support the continued study of dietary supplementation to enhance mammary gland health in dairy cows.

Use of a staphylococcal vaccine to reduce prevalence of mastitis and lower somatic cell counts in a registered Saanen dairy goat herd.

This investigation evaluated the efficacy of a bacterin in reducing the prevalence of staphylococcal mastitis and somatic cell counts (SCC) in a dairy goat herd. Does were vaccinated or left as controls, and the levels of mastitis and SCC monitored over 18 months. Staphylococcus caprae (42.5%), S. xylosus (15.1%), and S. simulans (10.0%) were the predominant causes of intramammary infections (IMI). The infection rate was 1.64 IMI/doe among vaccinates, which tended to be lower (P < 0.12) than controls (2.67 IMI/doe). The spontaneous cure rate of IMI after immunization was 1.28 cures/doe in vaccinates, which was higher than controls (0.6 cures/doe; P < 0.043). Average SCC of milk samples from vaccinates tended to be lower than that of controls (1274 × 10(3)/ml vs. 1529 × 10(3)/ml, respectively) (P < 0.10). Results support the continued study of mastitis vaccines for use in managing staphylococcal mastitis and SCC in dairy goats.

Effect of dietary supplementation on the antimicrobial activity of blood leukocytes isolated from Holstein heifers.

The purpose of this investigation was to evaluate the effect of an immunostimulating feed supplement (OmniGen-AF®) on the antimicrobial properties of blood leukocytes in dairy heifers in an attempt to prevent mastitis. Blood leukocytes from supplemented and unsupplemented controls were used. Phagocytic activity and reactive oxygen species (ROS) production were studied on d 0 (prior to feed supplementation) and on days 30 and 60 after supplementation. L-selectin and IL-8R mRNA expressions on blood leukocytes were evaluated on d 0 (prior to feed supplementation) and monthly thereafter for 15 mo. On d 30 after supplementation, neutrophils from treated heifers exhibited greater binding and internalization of Escherichia coli and greater ROS production compared with unsupplemented controls. L-selectin mRNA expression was increased in supplemented heifers vs. controls; however, IL-8R mRNA expression was not different. Results support the continued study of dietary supplementation as an additional management tool to enhance udder health in dairy heifers.

Influence of horn flies (Haematobia irritans) on teat skin condition, intramammary infection, and serum anti-S. aureus antibody titres in holstein heifers.

Staphylococcus aureus remains a major mastitis-causing pathogen in growing dairy heifers, resulting in damage to developing milk secretory tissue. The purpose of this study was to evaluate the role of horn flies as vectors in the spread of S. aureus among dairy heifers immunized with a S. aureus bacterin. We analyzed the prevalence of mastitis among quarters, evaluated teat skin condition (as a result of biting flies) prior to and after insecticide administration, and measured serum anti-S. aureus antibody titres monthly after vaccination. Response to S. aureus immunization was poor; however, titres increased 2- to 3-fold during the period when fly populations increased drastically and teat skin condition worsened, especially front quarter teat condition. Presence of flies and the resulting teat lesions were associated with a high level of S. aureus mastitis. Use of an insecticidal pour-on reduced fly populations and healed teat lesions, but existing cases of mastitis required antibiotic therapy.

Technical note: Development of a challenge model for Streptococcus uberis mastitis in dairy heifers.

A challenge model for experimentally inducing Streptococcus uberis mastitis in bred dairy heifers was developed. Qualifying heifers (n=7) exhibited antibody titers of <1:10,000 against Strep. uberis antigens and were free of intramammary infections (IMI). Two contralateral quarters of each heifer were assigned to receive an infusion of Strep. uberis (1,000 to 2,000 cfu); remaining quarters served as unchallenged controls. For a successful challenge and infection, 3 of 4 consecutive mammary secretion samples had to culture positive for Strep. uberis. Six of the 7 heifers were challenged successfully in both infused quarters with a mean dose of 1,080 cfu; once confirmed, infections were treated with a one-time infusion of nonlactating cow therapy. Before challenge, mammary secretion leukocyte counts averaged 8.4×10(6)/mL in all quarters. At 24h after challenge, leukocyte count increased to 18.4×10(6)/mL in challenged quarters, peaking on d 5 at 24.3×10(6)/mL; unchallenged quarters remained at ≤10.4×10(6)/mL, but increased to 15.2×10(6)/mL on d 7 and then decreased. Before challenge, macrophages predominated (81%) in mammary secretions followed by lymphocytes (15.3%) and neutrophils (3.7%). By 24h after challenge, neutrophils increased in challenged quarters and predominated for the duration of the trial (65.3 to 70%), whereas macrophages predominated in unchallenged control quarters (65.2 to 75.2%). The challenge model was successful in establishing Strep. uberis IMI in 85.7% of animals, and IMI were controlled (100% cure) by administering nonlactating cow therapy. All heifers calved free of IMI and antimicrobial residues, with milk production similar to that of herd mates and with somatic cell counts (SCC) <200,000 cells/mL.

Nitrogen metabolism and hormonal responses of steers fed wheat silage and infused with amino acids or casein.

Four Holstein steers (159 kg) surgically fitted with abomasal-infusion cannulas were used in a 4 x 4 Latin square study to test amino acid (AA) and casein (CAS) infusions on nitrogen balance and hormonal status of steers consuming vegetative wheat (Triticum aestivum L.) silage (12.3% CP). Treatments were 5-d infusions of 1) water (CONT), 2) arginine (ARG; 13.69 g/d), 3) limiting amino acids (LAA, 13.69 g/d arginine + 10.92 g/d histidine + 28.97 g/d lysine + 10.88 g/d methionine + 16.96 g/d threonine, and 4) Na-CAS (300 g/d). Whole blood was collected for plasma AA, growth hormone (GH), insulin, and IGF-I concentrations. Data were analyzed by ANOVA, and the following orthogonal contrasts were used to separate treatment means: CONT vs ARG; ARG vs LAA; and LAA vs CAS. Urinary N increased (P < .02) for CAS vs LAA. Arginine increased N retention, as did CAS, compared to LAA. Total plasma essential AA were decreased by arginine. Mean plasma insulin concentrations were increased by CAS (P < .034). Arginine increased mean plasma GH levels, but not IGF-I. The CAS treatment increased (P < .015) IGF-I levels, but not GH. These data suggest that performance of steers fed wheat silage was limited by duodenal AA flow and that arginine was the first-limiting AA. Casein infusion increased plasma insulin and IGF-I, which would explain the improved growth noted in calves and lambs fed forages supplemented with ruminally undegraded protein.